1. Technical Field of the Invention
The present invention relates generally to a method of braiding or twisting coil wires to make a coil assembly which may be employed in an electric rotary machine such as a motor-generator for automotive vehicles.
2. Background Art
There have been proposed a variety of methods of producing a coil assembly for use in electric rotary machines such as motor-generators. For example, Japanese Patent First Publication No. 2002-176752 teaches winding a plurality of coil wires simultaneously using a pair of winding strip cores. Japanese Patent First Publication No. 2004-104841 teaches how to braid a first coil wire and a second coil wire. Specifically, the first coil wire is turned through 90° around the axis of the second coil wire, as having been shaped into triangular waves in a winding process, and moved so as to make an overlap therebetween by half a turn, and also turned through 90° around the axis of the second coil wire. This sequence of steps is repeated to braid the first coil wire over the second coil wire by half a turn.
The braiding of coil wires each of which has a plurality of turned portions may also be achieved by turning a first coil wire around a second coil wire, like in conventional wire stranding machines, and moving the first coil wire by a coil pitch per turn or holding two coil wires crossed a given angle and rotating them around each other.
The above methods are, however, needed to keep the angle which the first and second coil wires make with each other as great as possible in order to avoid physical interference between the turned portions during the rotation of the first and second coil wires. This may result in undesirable deformation of straight portions of the first and second coil wires which are to be disposed inside slots of a stator core, which leads to a difficulty in shaping the braided coil wires into a desired geometry.